Luminaires are used for many lighting applications including outdoor lighting, general illumination, facade illumination, and feature illumination, for example, of statues and fountains. In these applications, dynamic colour lighting schemes may be implemented by controlling the operation of the lighting elements within the luminaires. One example of illuminating a building facade is described in EP-A-2116761 where multiple asymmetric beams produced by a group of light-emitting diode (LED) elements positioned under a lens unit are combined at the surface to be illuminated.
Luminaires may comprise an array or matrix of light-emitting diode (LED) elements having one or more colours, and, in multi-coloured luminaires, coloured LED elements, such as, red (R), green (G) and blue (B) LED elements placed close together in the array to provide output illumination for a surface. US-A-2005/213321 describes a full colour light source that uses R, G, B LED elements as a single light source, the LED elements being arranged in triplets, one for each colour.
The colour of the overall illumination provided by multi-coloured luminaires is produced by mixing the output of the R, G, B LED elements in different relative proportions. By changing the relative proportions of the light generated by the R, G and B LED elements, changes in the overall colour of the illumination are obtained. White (W) and amber (A) LED elements may also be used in addition to the conventional R, G and B elements. The relative ratios of the light output by the LED elements are controlled to define the base-colour brightness produced. Typically, the LED elements are arranged in regular patterns within the array, namely, as repeated lines or columns within the array. For example, a sequence of RGB, RGBW or RGBA colours can be repeated many times within the array.
One luminaire with coloured LED elements is described in WO-A-2010/004495 where LED triplets of R, G and B LED elements are used to provide illumination, each triplet being controlled to provide static white illumination as well as dynamic or general lighting that can be dimmed and changed in colour temperature. White and/or amber LED elements can be used with the triplets and can be individually dimmed to produce colours of the rainbow.
However, many coloured LED arrays used in luminaires tend to provide non-homogeneous and non-uniform illumination particularly around the edges of the light beam produced. Moreover, such coloured LED arrays tend not to be scalable as they are based on either a 3×3 module (where R, G and B LED elements only are used) or a 4×4 module (where R, G, B and W (or A) LED elements are used). Such modules cannot readily be repeated whilst maintaining a homogeneous and uniform output except in multiples of 4 modules, 9 modules, 16 modules, 25 modules etc. which provide luminaire arrays having a substantially square profile.